A stator core of a rotating electrical machine used for various applications in recent years is formed in a cylindrical shape by stacking a plurality of electromagnetic steel sheets and welding the stacked electromagnetic steel sheets together in the stacking direction. Such a stator core has the advantage that the manufacturing cost of the die is reduced, because the swages are not used in forming the stator core. Since the stator core is formed by welding, unfortunately, the plural electromagnetic steel sheets are electrically continuous with one another through the welded portions. As a result, the magnetic flux flowing from the rotor to the stator core interlinks with the welded portions, and the eddy current flows as the magnetic flux changes with time, which increases the eddy current loss.
Patent Literature 1 discloses that the welds are formed in the staggered fashion on the inner peripheral face of the stator core in the stacking direction of the stator core. The conventional technique of Patent Literature 1, which forms the staggered welds to suppress the influence of the interlinkage magnetic flux, that the eddy current loss, improves the operation efficiency of the rotating electrical machine.